<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>1.什么是环境与作用域</title>
</head>

<body>
  <script>
    // 全局变量 ,不会被回收
    let title = "后盾人";
    function show(){
      alert(title);
    }
    show(); //全局变量能渗透到函数的作用域里面
  </script>

</body>

</html>